The present invention relates to railroad freight cars and in particular to cars of the type incorporating a tall center beam structure extending along the length of the car body between a pair of bulkheads located at the ends of the car body.
Center beam railroad cars have been used for the past three decades to carry materials such as lumber and sheets of building material which can be contained in packages of uniform size and shape. Such railroad cars have repeatedly been redesigned in attempting to reduce tare weight yet provide ample strength to resist dead weight forces of lading as well as the dynamic forces produced by movement of such a car as a part of a train. Lighter weight in such cars advantageously allows carriage of additional revenue-bearing cargo while the laden car remains within limits on the maximum loading which can be imposed on the rails. Additionally, a lighter car requires less fuel when being moved unladen.
Various stages of development of such center beam cars are represented in prior art patents such as Wagner U.S. Pat. No. 3,734,031, Baker U.S. Pat. No. 4,543,887, Harris et al. U.S. Pat. No. 4,681,041, and Butcher et al. U.S. Pat. No. 4,802,420. The cars disclosed in these patents all include bulkheads at the opposite ends of a car body and an upright longitudinally-oriented center beam including the center sill of the car body, a top chord interconnecting the tops of the bulkheads, and a vertical structure interconnecting the center sill with the top chord along the length of the car body. In such previously known center beam cars a rigid vertical plate is attached to the bulkhead at each end of the car body and extends longitudinally toward the opposite end as part of the center beam. Such a vertical plate extends the entire length of the car in earlier center beam car designs, but in later center beam designs portions of the vertical plate were omitted, as shown in the Baker, Harris et al., and Butcher et al. patents mentioned above. It was still thought to be necessary to provide at least a short vertical plate, immediately adjacent the bulkhead, as shown in Butcher et al., to interconnect the bulkhead with the center beam rigidly and with enough strength to transfer loads from the upper portions of the center beam through the bulkhead to the center sill of the car, even though the weight of such a vertical plate was recognized as imposing a penalty on car lading capacity.
What is desired, then, is an improved center beam car of lighter weight than previously has been thought practical, yet which has ample strength to withstand the forces imposed by greater weights of lading than could be carried safely by previously-known cars.